1. Field of the Invention
The present invention relates to an exterior wall structure for buildings and structures that provides excellent rain protection, moisture permeability and breathability.
2. Description of the Related Art
Conventional building methods for forming an exterior wall structure for buildings such as wooden dwelling houses and the like can be roughly broken down into two types: a traditional wet (mortar) finish and a siding finish. With the popularization of a breathable vent layer construction method, siding finishes are becoming the mainstream method. However, wet finishing has also been receiving renewed interest as the building exterior walls are becoming more customized and multifaceted. It should be noted here that the terms exterior and interior are relative as to location within a structure, but it is understood that exterior refers to a location closer to the outside of a building whereas interior refers to a location closer to the inside of a building. Regardless of which construction method is used, for the durability of the building some measures are required to prevent any water leakage from the outside. For example, mortar finishes warrant a structure wherein a breathable waterproof sheet is attached to the exterior surface of an exterior wall base material, such as gypsum board, concrete, plywood, and the like and wherein on the exterior side thereof are mounted struts, studs, or fixed or random length furring strips, spaced at suitable intervals to generate a continuous vent layer over the entire surface of the waterproof-sheet-covered base material. Further, on top of the aforementioned structure, a lath screen is mounted, followed by applying cement mortar as an exterior wall material, thereby completing the exterior wall. It is known to be very difficult to completely prevent water leakages through cracks or from around window openings from aged mortar-based exterior walls. Further, for the breathable vent layer construction method, various proposals have been made for providing highly durable structures calling for mounting a vent layer between an exterior wall and an insulating material to prevent dew formation and degradation in performance of the structure material. However, none of these proposals has been completely satisfactory.
For example, Japanese Patent Application Publication Kokai H08-120799 discloses a technology which comprises providing a vent layer panel constituting a vent structure within the wall generated between an exterior and an internal wall of a building wherein the vent panel has vent layers or vent holes running therethrough in an in-plane direction and through-holes that run through in an out-plane direction and cross the vent layers or holes. Also disclosed is sheet having moisture permeability and wind-breaking properties, which sheet is attached to one of the surfaces of the panel.
Japanese Patent Application Publication Kokai 2001-20398 discloses a waterproof surface material that can effectively prevent internal condensation on an exterior wall, can minimize the number of parts associated with exterior work to simplify the detailing of the exterior, and does not lose any waterproofing function by attaching exterior parts or tacker nail holes and the like. The material can suppress the formation of cracks due to an imbalance in coated thicknesses of a wet type exterior finishing material, wherein an asphalt compound layer is provided between the exterior base material and exterior finished material, wherein one side of the asphalt compound layer is provided, opposite to the exterior wall base material, with an indented and protruded surface by spot-forming multiple protrusions, thereby assuring that the gap between these protrusions can act as a path for water vapor diffusion and effectively prevent any internal condensation in the exterior wall.